http://www.popularmechanics.com/automotive/how_to/4311498.html

The article explains why there are problems running high 
concentrations of biodiesel in newer diesel engines.

"...
And here is where the pitfall lies for biodiesel users like 
myself. Most of the manufactures decided to inject fuel into the 
cylinders just after the cylinder fires and the exhaust valve 
opens. At this point, the fuel vaporizes and the vapors move down 
the exhaust to the DPF and clean it. Because biodiesel is denser 
than conventional diesel fuel (it has a longer hydrocarbon chain) 
and has a higher distillation temperature and boiling point, it 
does not vaporize as easily. Some of the fuel ends up adhering to 
the cylinder wall and runs past the rings, diluting engine oil."



Best Wishes,
--
Gabriel L Espinosa